Radar attenuation mitigation

ABSTRACT

Techniques and apparatuses are described that enable radar attenuation mitigation. To improve radar performance, characteristics of an attenuator and/or properties of a radar signal are determined to reduce attenuation of the radar signal due to the attenuator and enable a radar system to detect a target located on an opposite side of the attenuator. These techniques are beneficial in situations in which the attenuator is unavoidably located between the radar system and a target, either due to integration within other electronic devices or due to an operating environment. These techniques save power and cost by reducing the attenuation without increasing transmit power or changing material properties of the attenuator.

BACKGROUND

Radars are useful devices that can detect and track objects, mapsurfaces, and display weather patterns. While radar is a common toolused in military and air traffic control operations, technologicaladvances are making it possible to integrate radars in electronicdevices. In many cases, a radar may replace bulky and expensive sensors,such as a camera, and provide improved performance in the presence ofdifferent environmental conditions, such as low lighting, motion, oroverlapping targets. While it may be advantageous to use the radar,there are many challenges associated with using radar in commercialdevices and commercial applications.

One such problem involves integrating and operating the radar in thepresence of an attenuator. The attenuator may include an exteriorhousing of the electronic device or another external material thatattenuates or distorts a radar signal. As available power may be limitedin small and mobile radar systems, compensating for the attenuation byincreasing the transmitted power may not be possible. As such, theattenuator degrades performance of the radar by decreasing an effectiverange, limiting the ability to detect smaller targets, and reducingtracking accuracy. Consequently, the effective operation and capabilityof the radar can be significantly reduced due to the attenuator, therebyfrustrating users or limiting the types of applications or environmentsthe radar can support.

SUMMARY

Techniques and apparatuses are described that enable radar attenuationmitigation. To improve radar performance, characteristics of anattenuator and/or properties of a radar signal are determined to reduceattenuation of the radar signal due to the attenuator and enable theradar system to detect a target located on an opposite side of theattenuator. These techniques are beneficial in situations in which theattenuator is unavoidably located between the radar system and a target,either due to integration within other electronic devices or due to anoperating environment. These techniques save power and cost by reducingthe attenuation without increasing transmit power or changing materialproperties of the attenuator.

Aspects described below include an apparatus comprising a radar systemand an attenuator. The radar system operates within a frequency rangeand a range of steering angles. The radar system transmits a radarsignal using a frequency of the frequency range and a steering angle ofthe range of steering angles to detect a target. The attenuator islocated between the radar system and the target. The attenuator has asemi-transparent material that attenuates the radar signal. Theattenuator is located at a distance from the radar system and has anon-zero thickness. The distance is a best distance within the range ofdistances and the non-zero thickness is a best thickness within therange of thicknesses. The best distance and the best thickness areeffective to mitigate attenuation of the radar signal to withinapproximately thirty percent of a minimum attenuation that exists acrossthe range of distances and the range of thicknesses for the frequency ofthe radar signal and the steering angle of the radar signal.

Aspects described below also include a system comprising an attenuatorand a radar system. The attenuator has a thickness and semi-transparentmaterial that attenuates a radar signal. The radar system is located ona side of the attenuator. The radar system determines a desiredfrequency and a desired steering angle of the radar signal based on thethickness of the attenuator and a distance between the attenuator andthe radar system. In addition, the radar system transmits the radarsignal using the desired frequency and the desired steering angleeffective to detect a target that is located on an opposite side of theattenuator.

Aspects described below also include a method comprising determining, bya radar system, a thickness of an attenuator that is located between theradar system and a target. The attenuator has a semi-transparentmaterial that attenuates a radar signal. The method also includesdetermining, by the radar system, a distance between the attenuator andthe radar system. Based on the thickness of the attenuator and thedistance between the attenuator and the radar system, a desiredfrequency and a desired steering angle of the radar signal thatmitigates attenuation of the radar signal through the attenuator isdetermined. Using the desired frequency and the desired steering angle,the method further includes transmitting the radar signal effective todetect the target through the attenuator.

Aspects described below also include a system comprising means fordetermining a characteristic of an attenuator or a property of a radarsignal to mitigate attenuation of the radar signal that passes throughthe attenuator.

BRIEF DESCRIPTION OF THE DRAWINGS

Apparatuses of and techniques enabling radar attenuation mitigation aredescribed with reference to the following drawings. The same numbers areused throughout the drawings to reference like features and components:

FIG. 1 illustrates an example environment in which radar attenuationmitigation can be implemented.

FIG. 2 illustrates an example radar system as part of a computingdevice.

FIG. 3 illustrates example techniques for adjusting a frequency of aradar signal or a distance between a radar system and an attenuator.

FIG. 4 illustrates example techniques for adjusting a steering angle ofa radar signal or a thickness of an attenuator.

FIG. 5 illustrates example graphs for optimizing radar attenuationmitigation.

FIG. 6 illustrates an example method for radar attenuation mitigation.

FIG. 7 illustrates an example computing system embodying, or in whichtechniques may be implemented that enable radar attenuation mitigation.

DETAILED DESCRIPTION

Overview

This document describes techniques and devices enabling radarattenuation mitigation. These techniques and devices are designed toimprove radar performance by mitigating attenuation and distortioneffects of an attenuator by determining characteristics of theattenuator or properties of a radar signal.

Typically a radar system includes a radome or some form of housingcomposed of a radio-frequency transparent material. The radome protectsthe radar's antennas from weather and debris, while minimallyattenuating a radar signal that passes through the radome. Whileelectronic devices can have external housings or protective cases thatcan protect an embedded radar system, these housings are not typicallydesigned for radar applications. In some cases, these housings are madeof materials that attenuate or distort the radar signal, therebydecreasing an effective range and accuracy of the radar system.

The attenuator presents a challenge for performing radar operationscompared to other forms of wireless communication. In one aspect, theradar signal passes through the attenuator twice, once duringtransmission and again during reception. Therefore, the attenuatordegrades the radar signal more than a one-way wireless communicationsignal. Furthermore, any changes in amplitude or phase of the radarsignal due to the attenuator directly impacts the radar system's abilityto determine location, movement, or characteristics of a target. Incontrast, wireless communication signals can utilize redundancy anderror correcting techniques to mitigate the effects of the attenuatorand reliably communicate information to other devices.

Instead of increasing transmit power or changing material properties ofthe attenuator, techniques for radar attenuation mitigation aredescribed. This document now turns to an example environment, afterwhich example systems, example methods, and an example computing systemare described.

Example Environment

FIG. 1 is an illustration of an example environment 100 in whichtechniques using, and an apparatus including, radar attenuationmitigation may be embodied. Environment 100 includes two devices andtechniques for using a radar system 102. In a first example, the radarsystem 102 is embedded in a computing device 104 that has an exteriorhousing 106. In a second example, the radar system 102 operates inside avehicle 108 that has a windshield 110.

The computing device 104 may use the radar system 102 to detect apresence of a user, map the user's face for authentication, track theuser's gestures for touch-free control, and so forth. To perform theseoperations, the radar system 102 transmits and receives a radar signal112. As the radar system 102 is integrated within the computing device104, the radar signal 112 passes through portions of the computingdevice 104, such as the exterior housing 106. In this example, theexterior housing 106 represents an attenuator 114 that is opaque orsemi-transparent to the radar signal 112. In other words, the attenuator114 decreases an amplitude of the radar signal 112 or distorts the radarsignal 112. In some cases, the attenuator 114 reflects a portion of theradar signal 112 (shown by reflected portion 116).

An amount of the reflected portion 116 is dependent upon properties ofthe radar signal 112 and characteristics of the attenuator 114. Exampleproperties of the radar signal 112 may include a frequency 118, asteering angle 120, a bandwidth, a beamshape, and so forth. Examplecharacteristics of the attenuator 114 may include a distance 122 betweenthe radar system 102 and the attenuator 114, a thickness 124 of theattenuator 114, material properties of the attenuator 114 such as adielectric constant, an orientation of the attenuator 114, and so forth.Assuming a transmit power of the radar system 102 is limited andre-designing the exterior housing 106 is not desirable, techniques forradar attenuation mitigation improves performance of the radar system102 by changing one or more of these attenuation-dependent propertiesand characteristics. As a result, the radar system 102 realizes betteraccuracy and larger effective ranges for detecting and tracking a target128 that is located on an opposite side of the attenuator 114.

Similarly, consider the vehicle 108, which includes the radar system 102mounted inside the vehicle 108 on the dashboard or on an inside of thewindshield 110. The vehicle 108 may use the radar system 102 forcollision avoidance, assisted driving, or, in the case of lawenforcement, detecting traffic violations. To perform these operations,however, the radar system 102 transmits and receives the radar signal112 through the windshield 110, which acts as the attenuator 114. Duringoperation, the radar system 102 may determine the distance 122 or thethickness 124 of the windshield 110 and adjust the frequency 118 or thesteering angle 120 to improve performance of the radar system 102. Insituations in which a location of the radar system 102 is generallyfixed relative to the attenuator 114, these determinations andadjustments can be made upon initialization of the radar system 102. Inother situations in which the radar system 102 is mobile (e.g., theradar system 102 is wearable by the user), these determinations can bemade multiple times during the operation of the radar system 102 andtherefore enable dynamic real-time adjustments by the radar system 102.

These techniques are beneficial in situations in which the attenuator isunavoidably located between the radar system 102 and the target 128,either due to integration within other electronic devices or due to theoperating environment. In addition, these techniques can be used tosupport mobile radar applications and can further assist inexperiencedusers in placing the radar system 102. Furthermore, these techniquessave power and reduce cost by improving radar performance withoutincreasing transmit power or changing material properties of theattenuator. As described in further detail below, many of thesetechniques can be performed during integration or operation of the radarsystem 102.

In more detail, consider FIG. 2, which illustrates the radar system 102as part of the computing device 104. The computing device 104 isillustrated with various non-limiting example devices including adesktop computer 104-1, a tablet 104-2, a laptop 104-3, a smailphone104-4, a computing watch 104-5, computing glasses 104-6, a gaming system104-7, a microwave 104-8, and a vehicle 104-9. The computing device 104can also include a home security system in which the radar system 102 ismounted inside a home to monitor an outside environment through awindow. Other devices may also be used, such as televisions, drones,track pads, drawing pads, netbooks, e-readers, home-automation andcontrol systems, and other home appliances. Note that computing device104 can be wearable, non-wearable but mobile, or relatively immobile(e.g., desktops and appliances).

The radar system 102 can be used as a stand-alone radar system or usedwith, or embedded within, many different computing devices 104 orperipherals, such as in control panels that control home appliances andsystems, in automobiles to control internal functions (e.g., volume,cruise control, or even driving of the car), or as an attachment to alaptop computer to control computing applications on the laptop.

The computing device 104 includes one or more computer processors 202and computer-readable media 204, which includes memory media and storagemedia. Applications and/or an operating system (not shown) embodied ascomputer-readable instructions on the computer-readable media 204 can beexecuted by the computer processors 202 to provide some of thefunctionalities described herein. The computer-readable media 204 alsoincludes a radar-based application 206, which uses radar data generatedby the radar system 102 to perform a function, such as gesture-basedcontrol, facial mapping, or user authentication. The radar-basedapplication 206 can also enable user control or configuration of theradar system 102. In some cases, the radar-based application 206 or thecomputer-readable media 204 stores pre-determined information regardingthe attenuator 114, such as the distance 122 or the thickness 124.

The computing device 104 may also include a network interface 208 forcommunicating data over wired, wireless, or optical networks. Forexample, the network interface 208 may communicate data over alocal-area-network (LAN), a wireless local-area-network (WLAN), apersonal-area-network (PAN), a wire-area-network (WAN), an intranet, theInternet, a peer-to-peer network, point-to-point network, a meshnetwork, and the like. The computing device 104 may also include adisplay (not shown).

The computing device 104, or an external object separate from thecomputing device 104, includes the attenuator 114 for which the radarsignal 112 passes through. In general, the attenuator 114 has a materialthat is opaque or semi-transparent to the radar signal 112. Theattenuator 114, for example, may be composed of a dielectric materialthat has a dielectric constant (e.g., relative permittivity) betweenapproximately four and ten. Example dielectric materials can includedifferent types of glass or plastics, some of which may be found withindisplay screens, exterior housings, or other components of the computingdevice 104. Assuming the computing device 104 is the smailphone 104-4,the attenuator 114 can include, for example, a glass display screen ofthe smailphone 104-4. Through absorption or reflection, the attenuator114 obstructs a portion of the radio signal 112. In some cases, thethickness 124 of the attenuator 114 can be set during manufacturing oradjusted by another attenuator 414 (illustrated in FIG. 4).

The radar system 102 is located on one side of the attenuator 114. Insome cases, a compliant layer that is substantially transparent to theradar signal 112 can be positioned between the radar system 102 and theattenuator 114. The compliant layer can include air, an air bladder,silicone, foam, a conformal lattice structure, and so forth. In othercases, a material layer made from adhesive, tape, or glue, can bepositioned between the radar system 102 and the attenuator 114. Thismaterial layer can assist with integrating the radar system 102 in thecomputing device 104 by enabling the distance 122 to be fined tuned.Furthermore, the material layer can assist in making the distance 122uniform across the physical dimensions of radar system 102. Inconsidering the manufacturing of multiple computing devices 104 thathave a radar system 102, the material layer can also reduce variationsin the distance 122 across the multiple computing devices 104, therebyenabling the multiple radar systems 102 to be similarly setup andimplement the techniques of radar attenuation mitigation based on thedistance 122. If the material layer also attenuates the radar signal 112(e.g., the material layer is semi-transparent to the radar signal 112),the material layer can further be used to fine tune the thickness 124 ofthe attenuator 114.

The radar system 102 includes a communication interface 210 to transmitthe radar data to a remote device, though this need not be used when theradar system 102 is integrated within the computing device 104. Ingeneral, the radar data provided by the communication interface 210 isin a format usable by the radar-based application 206.

The radar system 102 also includes one or more antennas 212 and atransceiver 214 to transmit and receive the radar signal 112. The radarsignal 112 can be steered or un-steered, wide or narrow, or shaped(e.g., hemisphere, cube, fan, cone, cylinder). The steering and shapingof the radar signal 112 can be achieved using analog or digitalbeamforming techniques and configured based on a size of the target 128or an estimated location of the target 128. Generally, the steeringangle 120 of the radar signal 112 represents a direction that a mainbeam is transmitted by the radar system 102 and includes both azimuthand elevation angles.

The radar system 102 can be configured for continuous wave or pulsedradar operations. A variety of modulations can be used, including linearfrequency modulation, stepped frequency modulations, and phasemodulations. The radar system 102 can be configured to emit microwaveradiation in a 1 GHz to 300 GHz range, a 3 GHz to 100 GHz range, andnarrower bands, such as 57 GHz to 63 GHz. In general, the radar system102 operates using a range of frequencies, a portion of which may beused for transmitting the radar signal 112 based on a center frequencyand a bandwidth.

The radar system 102 may also include one or more system processors 216and a system media 218 (e.g., one or more computer-readable storagemedia). The system media 218 includes an attenuation mitigator 220,which can configure the radar system 102 for operation in the presenceof the attenuator 114. For example, the attenuation mitigator 220 cansend commands to the transceiver 214 to control the frequency 118 or thesteering angle 120 of the radar signal 112. As another example, theattenuation mitigator 220 can prompt the user via the computing device.In some cases, the attenuation mitigator 220 receives the pre-determinedcharacteristic of the attenuator 114 that is stored in thecomputer-readable media 204 via the computing device 104. Alternatively,the attenuation mitigator 220 can process the radar signal 112 tomeasure one or more characteristics of the attenuator 114. In general,the attenuation mitigator 220 performs frequency selection, steeringangle selection, distance selection, or thickness selection to achievethe desired radar performance, as described in further detail withrespect to FIGS. 3 and 4.

FIG. 3 illustrates example techniques for adjusting the frequency 118 ofthe radar signal 112 or the distance 122 between the radar system 102and the attenuator 114. An example graph 302 plots an amplitude of theradar signal 112 versus the frequency 118 for different distances 122.Three example are considered, including a first distance 122-1 (shown bya solid line), a second distance 122-2 (shown by a dashed line), and asituation 304 without the attenuator 114 (shown by a dotted-dashedline). For illustration purposes, the graph 302 is not drawn to scale.

As shown by 304, the amplitude for different frequencies 118 isapproximately the same if the attenuator 114 is not present. Incontrast, the plots of the first distance 122-1 and the second distance122-2 show a peak amplitude of the radar signal 112 is reduced due tothe presence of the attenuator 114. The peak amplitude for the firstdistance 122-1, for example, may be approximately 0.5 decibels (dB) lessthan the amplitude shown by 304. Furthermore, the amplitude varies basedon the frequency 118, which can differ by approximately 0.5 dB to 10 dBwith respect to 304. In comparing the attenuation between the firstdistance 122-1 and the second distance 122-2, some frequenciesexperience more or less attenuation due to the attenuator 114.

The variation in the amplitude across different frequencies 118 alsocauses spectral distortion of the radar signal 112. Consider, forexample, that the radar system 102 selects a center frequency and abandwidth for performing frequency modulation. However, at least aportion of the selected frequencies are significantly attenuated by theattenuator 114 compared to the other portion of the selectedfrequencies. In this situation, the attenuator 114 produces a windoweffect that reduces an effective bandwidth of the radar signal 112.Consequently, a total signal-to-noise ratio of the radar signal 112 isreduced, which further degrades radar performance.

A first technique determines the frequency 118 based on the distance122. For example, a first frequency selection 306-1 can be chosen forthe first distance 122-1 and a second frequency selection 306-2 can bechosen based for the second distance 122-2 to achieve a desiredamplitude of the radar signal 112. Consider if the radar system 102 isintegrated within the computing device 104, the first frequencyselection 306-1 can represent a range of frequencies from approximately60 to 62 gigahertz (GHz) for the first distance 122-1 of approximately0.25 millimeters (mm) and the second frequency selection can represent arange of frequencies from approximately 59 to 61 GHz for the seconddistance 122-2 of 0.75 mm. If the distance 122 is substantially fixed,pre-determined, and stored in the computer-readable media 204, theattenuation mitigator 220 can select the frequency 118 based on thedistance 122. In other situations, the attenuation mitigator 220 canmeasure the distance 122 and automatically determine the frequency 118.Based on the frequency selection 306 and the attenuation amount, theattenuation mitigator 220 can also sub-divide and rank the frequencies118 into multiple bandwidths and center frequencies, to supportfrequency diversity, Doppler blind avoidance, and interferenceavoidance.

In some cases, the radar system 102 may have a limited range offrequencies 118 that are available during operation either by design ordue to other types of operational factors, such as those mentionedabove. A second technique determines the distance 122 based on thefrequency 118. If the desirable operating frequency range is, forexample, between approximately 59 GHz and 61 GHz, the distance can beset to approximately 0.5 mm to improve the amplitude of the radar signal112. Consider if the radar system 102 is integrated within the computingdevice 104, the distance 122 can be set to the desired amount duringfabrication. In some cases, the radar system 102 may be mounted to amovable platform 308 that can adjust the distance 122 automatically viathe attenuation mitigator 220. The movable platform 308 may include apiezoelectric material, a movable microplatform, a spring or gear-drivenplatform, and so forth. If the attenuator 114 is external to thecomputing device 104 and the radar system 102 is mobile, the attenuationmitigator 220 can prompt the user via the radar-based application 206 tomove the radar system 102 and adjust the distance 122, thereby improvingradar performance.

FIG. 4 illustrates example techniques for adjusting the steering angle120 of the radar signal 112 or the thickness 124 of the attenuator 114.An example graph 402 plots the amplitude of the radar signal 112 versusthe steering angle 120 for different thicknesses 124. Three examples areconsidered, including a first thickness 124-1 (shown by a dashed line),a second thickness 124-2 (shown by a dashed line), and a situation 404without the attenuator 114 (shown by a dotted-dashed line). Forillustration purposes, the graph 402 is not drawn to scale.

As shown by 404, the amplitude for different steering angles 120 isapproximately the same across a wide range of steering angles 120 if theattenuator 114 is not present. This range may include, for example,steering angles 120 between approximately −45 and 45 degrees. Incontrast, the plots of the first thickness 124-1 and the secondthickness 124-2 show smaller amplitudes of the radar signal 112. In somecases, the reduction in amplitude can be approximately 10 dB or more.Furthermore, the range of steering angles 120 for which the amplitudedoes not significantly change can be smaller due to the attenuator 114,such as between −30 and 30 degrees. A third technique determines thesteering angle 120 or an angle selection 406 for the radar signal 112based on the thickness 124. In some cases, the radar system 102 can beangled relative to an anticipated target location such that the desiredsteering angle 120 can be used to detect the target 128.

As seen in the graph 402, the amplitude of the radar signal 112 may alsovary based on the thickness 124 of the attenuator 114. In someimplementations, increasing the thickness 124 decreases reflection ofthe radar signal 112. For example, the thickness 124 of the exteriorhousing 106 can be increased from approximately 0.5 mm to 1.0 mm, whichcauses the attenuation to decrease by at least approximately 0.5 dB. Thethickness 124 of the exterior housing 106 can be set to the desiredvalue during fabrication, by applying another attenuator 414 to a sideof the exterior housing 106 (e.g., a layer of adhesive, tape, or glue),or by attaching another attenuator 414 (e.g., a protective case). Ingeneral, applying or attaching the other attenuator 414 increases aneffective thickness of the attenuator 114. The attenuation mitigator 220can also prompt the user via the radar-based application 206 to applythe other attenuator 414. In some cases, the thickness 124 of theattenuator 114 can be adjusted across an area through which the radarsystem 102 is expected to direct the radar signal 112.

In general, the attenuation of the radar signal 112 depends on thefrequency 118 of the radar signal 112, the distance 122 between theradar system 102 and the attenuator 114, the steering angle 120 of theradar signal 112, and the thickness 124 of the attenuator 114. Thetechniques for radar attenuation mitigation enable one or more of theseabove-mentioned parameters to be adjusted, thereby mitigating theeffects of the attenuator 114 and achieving the desired amplitude thatenables the radar system 102 to detect the target 128 with a desiredaccuracy and effective range. As described in the examples above, thewidest range of frequencies 118, the widest range of steering angles120, the closest distance 122, or the smallest thickness 124 may not bedesirable when the radar system 102 is in the presence of the attenuator114. However, by balancing each of these parameters, a desired value ofthe frequency 118, the steering angle 120, the distance 122, and thethickness 124 can be determined to support radar operations withoutincreasing the transmit power. Sometimes one or more of theseattenuation-dependent characteristics and properties are fixed orconstrained and can be used to determine the other attenuation-dependentcharacteristics and properties.

FIG. 5 illustrates example graphs for optimizing radar attenuationmitigation. As explained above, any one or more of the above-mentionedcharacteristics and parameters can be adjusted to achieve the desiredamount of attenuation and enable the radar system 102 to detect thetarget 128 through the attenuator 114. In other words, a four-variablesolution exists, in which the frequency 118 of the radar signal 112, thedistance 122 between the radar system 102 and the attenuator 114, thesteering angle 120 of the radar signal 112, or the thickness 124 of theattenuator 114 are chosen to mitigate the attenuation.

Consider a simulation that generates amplitude plots for differentvalues of the four variables. Constraints can be placed on these fourvariables for determining a maximum possible amplitude. If theattenuator 114 is the exterior housing 106 of FIG. 1, for example, thethickness of the exterior housing 106 can be constrained by a desiredexterior housing strength and an ergonomic size or weight of thecomputing device 104. Additionally, if the radar system 102 isintegrated within the computing device 104, the distance 122 may beconstrained based on manufacturing techniques and a desired size of thecomputing device 104. In some cases, the frequencies 118 may beconstrained by hardware of the radar system 102 or operating conditions,such as to avoid interfering with another radar system 102. Furthermore,the steering angles 120 may be constrained to reduce angular ambiguitiesor to avoid illuminating other components in the computing device 104 orother external objects. In the situation described above, exampleconstraints may include the thickness 124 being between approximately0.2 mm to 2 mm, the distance 122 being between approximately 0 mm to 5mm, the frequency being approximately 30 GHz or between a range offrequencies, such as between approximately 58 to 60 GHz, and thesteering angle 120 being between approximately −45 to 45 degrees.

Using these constraints, the simulation produces results that can beused to select the frequency 118, the steering angle 120, the distance122, and the thickness 124 based on the maximum possible amplitude. FIG.5 depicts three example graphs 502, 504, and 506, which representpossible amplitudes of the radar signal 112 through the attenuator 114for a fixed transmission power. The axes of the graphs 502-506 representa range of thicknesses 124 and a range of distances 122. Each of thethree graphs 502-506 also correspond to different frequencies (e.g.,frequencies 118-1, 118-2, and 118-3) and steering angles (e.g., steeringangles 120-1, 120-2, and 120-3). Within these graphs, peaks and valleysrespectively indicate values of the variables that provide a higheramplitude or a lower amplitude. For example, peak 508 identifies adesired distance 122 and a desired thickness 124 for the frequency 118-1and the steering angle 120-1 that provides a maximum amplitude.

Based on the graphs 502-506, the frequency 118, the steering angle 120,the distance 122, and the thickness 124 can be determined to achieve thedesired amplitude. In general, the desired amplitude may be representedby a percentage of a maximum amplitude. As an example, the percentagemay be between approximately 0% to 50% of the peak 508. In terms ofattenuation, the variables can be chosen to achieve an attenuation thatis within approximately 0% to 50% of a minimum attenuation, including10%, 20%, 30%, and so forth. Accordingly, the techniques for radarattenuation mitigation enable the attenuation to be reduced to within adesired percentage of the maximum amplitude or the minimum attenuationbased on the chosen constraints.

While some of the techniques may be implemented during fabrication orintegration of the radar system 102 within the computing device 104,other techniques can be implemented during operation of the radar system102, as described with respect to FIG. 6.

Example Methods

FIG. 6 depicts an example method 600 for operating the radar system 102in the presence of the attenuator 114. Method 600 is shown as sets ofoperations (or acts) performed but not necessarily limited to the orderor combinations in which the operations are illustrated. Further, any ofone or more of the operations may be repeated, combined, reorganized, orlinked to provide a wide array of additional and/or alternate methods.In portions of the following discussion, reference may be made toenvironment 100 of FIG. 1 and entities detailed in FIG. 2, reference towhich is made for example only. The techniques are not limited toperformance by one entity or multiple entities operating on one device.

At 602, a thickness of an attenuator that is located between a radarsystem and a target is determined by the radar system. The attenuatorhas a semi-transparent material that attenuates radio frequencies. Thethickness, for example, can include the thickness 124 of the attenuator114.

At 604, a distance between the attenuator and the radar system isdetermined by the radar system. The distance, for example can includethe distance 122 between the attenuator 114 and the radar system 102.Depending on the situation, the thickness 124 and the distance 122 at602 and 604 can be indirectly or directly determined by the radar system102.

Consider if the radar system 102 is embedded within the computing device104 of FIG. 1. During assembly, the distance 122 of the radar system 102from the exterior housing 106 may be fixed as well as the thickness 124of the exterior housing 106. In this situation, the characteristic ofthe attenuator 114 may be pre-determined and stored in the system media218 of the radar system 102 or the computer-readable media 204 of thecomputing device 104. As such, the radar system 102 can indirectlydetermine the characteristic by accessing or receiving thepre-determined characteristic.

As another example, consider if a user attaches a separate protectivecase to the computing device 104 that effectively increases thethickness 124 of the exterior housing 106. In this case, the attenuationmitigator 220 can directly determine the characteristic by analyzing thereflected portion 116 of the radar signal 112. The attenuation mitigator220 may initiate a calibration procedure that transmits a dedicatedradar signal. Alternatively, the attenuation mitigator 220 can processreturns from other radar signals that are designed for detecting ortracking the target 128.

The direct method is also advantageous for situations in which theoperating environment may vary, such as when the attenuator 114 isseparate from the computing device 104 and the radar system 102 or theradar system 102 is mobile. As an example, consider the situation inwhich the user places a radar-based security system inside a house or aradar-based driving assistance system inside the vehicle 108 of FIG. 1.The radar system 102 can use the direct method to automatically measurethe distance 122 or the thickness 124 of the attenuator 114 in thesesituations. The attenuation mitigator 220 can also record the determinedcharacteristic of the attenuator 114 in the system media 218 for futurereference.

At 606, a desired frequency and a desired steering angle of the radarsignal that mitigates attenuation of the radar signal through theattenuator is determined based on the thickness of the attenuator andthe distance between the attenuator and the radar system. Theattenuation mitigator 220, for example, can select a range offrequencies 118 and a range of steering angles 120 that reduceattenuation and spectral distortion caused by the attenuator 114. Theseproperties are useful for improving performance of the radar system 102without adjusting the transmit power. In situations in which thedistance 122 or the thickness 124 are adjustable, the attenuationmitigator 220 can also send commands to adjust these characteristics,such as by commanding the movable platform 308 or prompting the user viathe radar-based application 206.

At 608, the radar signal is transmitted using the desired frequency andthe desired steering angle effective to detect the target through theattenuator. For example, the attenuation mitigator 220 can send commandsto the transceiver 214 for setting a center frequency, a bandwidth, anazimuth, or an elevation of the radar signal 112. In general, thedetermined property of the radar signal 112 adjusts the attenuation to adesired amount to enable the target 128 to be detected within a desiredoperating range of the radar system 102. By reducing the attenuation,accuracy of the radar system 102 increases, thereby enabling the radarsystem 102 to support a variety of applications, including userauthentication, gesture control, vehicle collision avoidance, securitymonitoring, and so forth. The method 600 can also be adapted for othercharacteristics of the attenuator 114 and properties of the radar signal112 as mentioned above. Furthermore, these techniques facilitateintegration of the radar system 102 within the computing device 104 aswell as user operation of the radar system 102 in a variety ofenvironments that include attenuators 114.

Example Computing System

FIG. 7 illustrates various components of example computing system 700that can be implemented as any type of client, server, and/or computingdevice as described with reference to the previous FIGS. 1 and 2 toimplement radar attenuation mitigation.

The computing system 700 includes communication devices 702 that enablewired and/or wireless communication of device data 704 (e.g., receiveddata, data that is being received, data scheduled for broadcast, datapackets of the data). The device data 704 or other device content caninclude configuration settings of the device, media content stored onthe device, and/or information associated with a user of the device.Media content stored on the computing system 700 can include any type ofaudio, video, and/or image data. The computing system 700 includes oneor more data inputs 706 via which any type of data, media content,and/or inputs can be received, such as human utterances, characteristicsof the attenuator 114 or information regarding integration of the radarsystem 102 within the computing system 700, user-selectable inputs(explicit or implicit), messages, music, television media content,recorded video content, and any other type of audio, video, and/or imagedata received from any content and/or data source.

The computing system 700 also includes communication interfaces 708,which can be implemented as any one or more of a serial and/or parallelinterface, a wireless interface, any type of network interface, a modem,and as any other type of communication interface. The communicationinterfaces 708 provide a connection and/or communication links betweenthe computing system 700 and a communication network by which otherelectronic, computing, and communication devices communicate data withthe computing system 700.

The computing system 700 includes one or more processors 710 (e.g., anyof microprocessors, controllers, and the like), which process variouscomputer-executable instructions to control the operation of thecomputing system 700 and to enable techniques for, or in which can beembodied, radar attenuation mitigation. Alternatively or in addition,the computing system 700 can be implemented with any one or combinationof hardware, firmware, or fixed logic circuitry that is implemented inconnection with processing and control circuits which are generallyidentified at 712. Although not shown, the computing system 700 caninclude a system bus or data transfer system that couples the variouscomponents within the device. A system bus can include any one orcombination of different bus structures, such as a memory bus or memorycontroller, a peripheral bus, a universal serial bus, and/or a processoror local bus that utilizes any of a variety of bus architectures.

The computing system 700 also includes a computer-readable media 714,such as one or more memory devices that enable persistent and/ornon-transitory data storage (i. e., in contrast to mere signaltransmission), examples of which include random access memory (RAM),non-volatile memory (e.g., any one or more of a read-only memory (ROM),flash memory, EPROM, EEPROM, etc.), and a disk storage device. A diskstorage device may be implemented as any type of magnetic or opticalstorage device, such as a hard disk drive, a recordable and/orrewriteable compact disc (CD), any type of a digital versatile disc(DVD), and the like. The computing system 700 can also include a massstorage media device (storage media) 716.

The computer-readable media 714 provides data storage mechanisms tostore the device data 704, as well as various device applications 718and any other types of information and/or data related to operationalaspects of the computing system 700. For example, an operating system720 can be maintained as a computer application with thecomputer-readable media 714 and executed on the processors 710. Thedevice applications 718 may include a device manager, such as any formof a control application, software application, signal-processing andcontrol module, code that is native to a particular device, a hardwareabstraction layer for a particular device, and so on.

The device applications 718 also any include system components, engines,or managers to implement radar attenuation mitigation. In this example,device applications 718 include the radar-based application 206 and theattenuation mitigator 220.

CONCLUSION

Although techniques using, and apparatuses including, radar attenuationmitigation have been described in language specific to features and/ormethods, it is to be understood that the subject of the appended claimsis not necessarily limited to the specific features or methodsdescribed. Rather, the specific features and methods are disclosed asexample implementations of radar attenuation mitigation.

What is claimed is:
 1. An apparatus comprising: a computing devicehaving an exterior housing; a movable platform; an attenuator, theattenuator located between a radar system and a target, the attenuatorcomprising at least a portion of the exterior housing and having asemi-transparent material that attenuates a radar signal, the attenuatorlocated at the distance from the radar system and having a non-zerothickness; and the radar system, the radar system located within theexterior housing of the computing device, mounted to the movableplatform, and configured to: operate within a frequency range and arange of steering angles; transmit the radar signal using a frequency ofthe frequency range and a steering angle of the range of steering anglesto detect the target; and dynamically adjust, during operation of theradar system, the distance from the radar system to the attenuator, thedynamic adjustment of the distance being effective to mitigateattenuation of the radar signal to be between a minimum attenuation andapproximately thirty percent above the minimum attenuation that existsacross a range of distances and a range of thicknesses for the frequencyof the radar signal and the steering angle of the radar signal.
 2. Theapparatus of claim 1, wherein: the range of distances includesapproximately 0 millimeters to 5 millimeters; and the range ofthicknesses includes approximately 0.2 millimeters to 2 millimeters. 3.The apparatus of claim 1, wherein the attenuator comprises a dielectricmaterial having a dielectric constant between approximately four andten.
 4. The apparatus of claim 3, wherein the dielectric materialincludes a glass material.
 5. The apparatus of claim 1, furthercomprising: another attenuator located between the radar system and thetarget, the other attenuator having another semi-transparent materialthat attenuates the radar signal, and wherein: the non-zero thickness ofthe attenuator includes the thickness of the other attenuator.
 6. Theapparatus of claim 5, wherein the other attenuator comprises aprotective case enclosing at least a portion of the exterior housing ofthe computing device.
 7. The apparatus of claim 1, wherein: the radarsystem is configured to transmit another radar signal using anotherfrequency of the frequency range and the steering angle; and the radarsystem is configured to adjust the distance between the radar system andthe attenuator to a particular distance within the range of distances,the particular distance being effective to mitigate the attenuation ofthe other radar signal to be between another minimum attenuation andapproximately thirty percent above the other minimum attenuation thatexists across the range of distances and the range of thicknesses forthe other frequency of the radar signal and the steering angle of theother radar signal.
 8. A system comprising: a vehicle having awindshield; an attenuator having a thickness and a semi-transparentmaterial that attenuates a radar signal, the attenuator comprising atleast a portion of the windshield; and a radar system located inside thevehicle and on a side of the attenuator, the radar system configured to:dynamically determine, during operation of the radar system, a desiredfrequency and a desired steering angle of the radar signal based on thethickness of the attenuator and a distance between the attenuator andthe radar system; and transmit the radar signal using the desiredfrequency and the desired steering angle effective to detect a targetlocated on an opposite side of the attenuator.
 9. The system of claim 8,wherein the desired frequency and the desired steering angle enables theradar system to detect the target through the attenuator withoutincreasing a transmit power of the radar system.
 10. The system of claim8, wherein the radar system is further configured to: measure thedistance between the radar system and the windshield; and determine,based on the measured distance, the desired frequency of the radarsignal that mitigates attenuation of the radar signal through theattenuator to be between a minimum attenuation for the measured distanceand approximately thirty percent above the minimum attenuation.
 11. Thesystem of claim 8, wherein the radar system is further configured to:measure the thickness of the windshield; and determine, based on themeasured thickness, the desired steering angle of the radar signal thatmitigates attenuation of the radar signal to be between a minimumattenuation for the measured thickness and approximately thirty percentabove the minimum attenuation.
 12. The system of claim 8, wherein: theradar signal includes a frequency modulated radar signal; and thedesired frequency includes a range of desired frequencies that reducespectral distortion of the radar signal based on the distance betweenthe attenuator and the radar system.
 13. A method comprising:determining, by a radar system located inside a vehicle, a thickness ofan attenuator that is located between the radar system and a target, thevehicle having a windshield, the attenuator comprising the windshieldand having a semi-transparent material that attenuates a radar signal;determining, by the radar system, a distance between the attenuator andthe radar system; dynamically determining, during operation of the radarsystem and based on the thickness of the attenuator and the distancebetween the attenuator and the radar system, a desired frequency and adesired steering angle of the radar signal that mitigates attenuation ofthe radar signal through the attenuator; and transmitting the radarsignal using the desired frequency and the desired steering angleeffective to detect the target through the attenuator.
 14. The method ofclaim 13, wherein: the desired frequency comprises a frequency within arange of frequencies; the desired steering angle comprises a steeringangle within a range of steering angles; and the desired frequency andthe desired steering angle being effective to mitigate the attenuationof the radar signal to be between a minimum attenuation andapproximately thirty percent above the minimum attenuation that existsacross the range of frequencies and the range of steering angles for thethickness of the attenuator and the distance between the attenuator andthe radar system.
 15. The method of claim 13, wherein determining thethickness of the attenuator and determining the distance between theattenuator and the radar system includes performing, by the radarsystem, a calibration procedure that measures, using another radarsignal, the thickness of the attenuator and the distance between theattenuator and the radar system.
 16. The method of claim 15, furthercomprising prompting a user to adjust the distance between the radarsystem and the attenuator by moving the radar system to a desireddistance within a range of distances, the desired distance beingeffective to mitigate the attenuation of the radar signal to be betweena minimum attenuation and approximately ten percent above the minimumattenuation that exists across the range of distances for the thicknessof the attenuator, the desired frequency, and the desired steeringangle.
 17. The method of claim 15, further comprising prompting a userto increase the thickness of the attenuator by positioning anotherattenuator between the radar system and the target to achieve a desiredthickness within a range of thicknesses, the desired thickness beingeffective to mitigate the attenuation of the radar signal through theattenuator and the other attenuator to be between a minimum attenuationand approximately ten percent above the minimum attenuation that existsacross the range of thicknesses for the distance between the radarsystem and the attenuator, the desired frequency, and the desiredsteering angle.
 18. The apparatus of claim 1, wherein the radar systemis further configured to, in response to a change in the thickness ofthe attenuator or the frequency range and the range of steering anglesthe radar system operates within, to provide an alert, via the computingdevice, to locate the radar system at a second distance from theattenuator, the second distance effective to maintain attenuation of theradar signal to be between a minimum attenuation and approximatelythirty percent above the minimum attenuation that exists across therange of distances and the range of thicknesses for the frequency of theradar signal and the steering angle of the radar signal.
 19. The systemof claim 8, wherein the radar system is further configured to:determine, based on the distance between the attenuator and the radarsystem and the thickness of the attenuator, a desired range offrequencies for the desired steering angle, transmit the radar signalusing the desired range of frequencies and the desired steering angleeffective to avoid interference, avoid a Doppler blind zone, or supportfrequency diversity.
 20. The system of claim 8, wherein the radar systemis mounted to a movable platform, the radar system is configured toadjust the distance between the radar system and the attenuator toanother distance within a range of distances, the other distance beingeffective to mitigate the attenuation of the radar signal to be betweena minimum attenuation and approximately thirty percent above the minimumattenuation that exists across the range of distances for the desiredfrequency and the desired steering angle of the radar signal.